replacing the air cooled to centrifugal chiller. - Page 4
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  1. #40
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    Don't get % RLA confused with % capacity. There 2 differant things.

  2. #41
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    Mixing oil and fire with a big spoon.
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    let's keep in mind the difference between RLA and Tonnage. despite what every BAS guy on the planet thinks, they are not the same thing nor is there a 1 to 1 correlation...not even at '100%'.

    as for a multi-compressor system versus a single compressor system, sure a multi-compressor system is going to have a better turn down ratio than a single compressor system, but there are many other factors to consider as well, such as barrel heat transfer rates...the air cooled compressor barrels (that just about every manufacturer uses) have very poor heat transfer compared to just about everybodys centrifugal evaporators...with this factored in, the turn down ratio may not be nearly as significant as it at first seems.

    other things to think about are the 2 unit (or more) arrangement. at first this system seems to favor a 2 unit (6 compressors total, RTAC-250, 50 Hz) system, however, this brings up how the unit is piped.

    piped in parallel, the maximum flow rate is 1,243 GPM per unit (2,486 GPM total). When the load is low, you will be cycling 2 compressors ON and OFF instead of 1 compressor ON and OFF with a sinlge package unit (centrifugal or air cooled screw)...not nearly as much turn-down-ratio as one would think.

    with the chillers piped in series, you have the limitation of 1,243 GPM...less cycling but less range of total flow rate...minimum is 339 GPM per chiller.

    lots to think about.
    You either love bacon or you are wrong.

    4 gallons of gas, 2 miles of travel, teaching my daughters how to drive in the high school parking lot...priceless!

  3. #42
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    Quote Originally Posted by R123 View Post
    Don't get % RLA confused with % capacity. There 2 differant things.
    was i working on my post so long that you beat me to it??? man, i have got to shorten my answers. probably won't happen though!
    You either love bacon or you are wrong.

    4 gallons of gas, 2 miles of travel, teaching my daughters how to drive in the high school parking lot...priceless!

  4. #43
    Join Date
    Mar 2003
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    my response was actually leaning toward a single package, evap condensing machine, with multiple screws that can do the 500 tons. Single evaporater, no series flow or isolation valves to shut one down on low load, just simple, straight forward chiller package. Yes it exists, and yes it can include pumps, vfd's etc all in one platform. total plant kw would be in the .8kw/ton range, and be rigged to the roof in one shot. there are other thingsa ut there than a trane rtac.

  5. #44
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    Dallas ,Texas
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    Quote Originally Posted by flange View Post
    my response was actually leaning toward a single package, evap condensing machine, with multiple screws that can do the 500 tons. Single evaporater, no series flow or isolation valves to shut one down on low load, just simple, straight forward chiller package. Yes it exists, and yes it can include pumps, vfd's etc all in one platform. total plant kw would be in the .8kw/ton range, and be rigged to the roof in one shot. there are other thingsa ut there than a trane rtac.

    You thinking Epak or Chillpak?

  6. #45
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    Jul 2011
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    East coast USA
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    well i would be curious to find out what direction they went. it would be nice to hear back from those who posted once in a while..

  7. #46
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    Aug 2006
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    Quote Originally Posted by flange View Post
    ...there are other thingsa ut there than a trane rtac.
    i know...i only had access to trane equipment specs and he had 2 trane rtaa's already.
    You either love bacon or you are wrong.

    4 gallons of gas, 2 miles of travel, teaching my daughters how to drive in the high school parking lot...priceless!

  8. #47
    Join Date
    Jan 2009
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    Keokuk, IA
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    Sometimes you have to go with where you can get the best service and support. In my area, Trane is pretty much it at the industrial level. Even at the commercial level, they are doing most of the support for all makes.

  9. #48
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    Mar 2003
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    nope. anudder company that makes semi custom stuff and refrigidation stuff, lol.

  10. #49
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    Feb 2008
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    Dubai
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    Dears,

    York engineers visited the site, they would submit the proposals and their advice in this regards.
    As I get the comments from York, I would update you.

    Moideen-DIRE

  11. #50
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    Aug 2003
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    Fort Worth, TX
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    Quote Originally Posted by R123 View Post
    Don't get % RLA confused with % capacity. There 2 differant things.
    Yep.
    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

  12. #51
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,273
    GPM * ∆T/24 = actual capacity

    So, if you have a machine rated at 250 tons and is flowing 600 GPM @ 7 degrees ∆T, its real time capacity is 175 tons. This would be ~87% of its nominal capacity. If the entering condenser water temp is below the nominal, say <85F ECWT, when this same chiller is producing 175 tons, the % RLA will be lower than it would be if the entering condenser water temp was 85F. This has to do with the pressure differential between condenser and cooler, and how much work the compressor must do to overcome that difference.
    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

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